@stdlib/stats-base-dists-exponential-logpdf
v0.2.2
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Natural logarithm of the probability density function (PDF) for an exponential distribution.
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Logarithm of Probability Density Function
Evaluate the natural logarithm of the probability density function (PDF) for an exponential distribution.
The probability density function (PDF) for an exponential random variable is
where λ
is the rate parameter.
Installation
npm install @stdlib/stats-base-dists-exponential-logpdf
Usage
var logpdf = require( '@stdlib/stats-base-dists-exponential-logpdf' );
logpdf( x, lambda )
Evaluates the natural logarithm of the probability density function (PDF) for an exponential distribution with rate parameter lambda
.
var y = logpdf( 2.0, 0.3 );
// returns ~-1.804
y = logpdf( 2.0, 1.0 );
// returns ~-2.0
If provided NaN
as any argument, the function returns NaN
.
var y = logpdf( NaN, 0.0 );
// returns NaN
y = logpdf( 0.0, NaN );
// returns NaN
If provided lambda < 0
, the function returns NaN
.
var y = logpdf( 2.0, -1.0 );
// returns NaN
logpdf.factory( lambda )
Returns a function for evaluating the natural logarithm of the probability density function (PDF) for an exponential distribution with rate parameter lambda
.
var mylogpdf = logpdf.factory( 0.1 );
var y = mylogpdf( 8.0 );
// returns ~-3.103
y = mylogpdf( 5.0 );
// returns ~-2.803
Notes
- In virtually all cases, using the
logpdf
orlogcdf
functions is preferable to manually computing the logarithm of thepdf
orcdf
, respectively, since the latter is prone to overflow and underflow.
Examples
var randu = require( '@stdlib/random-base-randu' );
var logpdf = require( '@stdlib/stats-base-dists-exponential-logpdf' );
var lambda;
var x;
var y;
var i;
for ( i = 0; i < 10; i++ ) {
x = randu() * 10.0;
lambda = randu() * 10.0;
y = logpdf( x, lambda );
console.log( 'x: %d, λ: %d, ln(f(x;λ)): %d', x, lambda, y );
}
Notice
This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.
For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.
Community
License
See LICENSE.
Copyright
Copyright © 2016-2024. The Stdlib Authors.